This invention relates to microbrushes, and, in particular, to injection molded brushes which are used during an endodontic or root canal procedure to more predictably clean the root canal system prior to obturation.
Following tooth maturation, the dental pulp is harbored within the structural elements of the tooth. Frequently, and for a variety of reasons, the pulp is irreversibly injured, resulting in inflammatory and infectious conditions which often adversely affect the tooth, its supporting structures, and the patient's health. Clinically, as an alternative to extraction, root canal treatment is performed and ideally directed towards the elimination of pulp, bacteria, and related irritants from the root canal system, followed by three-dimensionally filling the root canal space with an inert, biocompatible, dimensionally stable, filling material, such as gutta percha. The obturation procedures will fill not just the main canal, but the fins, webs, cul-de-sacs, lateral canals, and all portals of exit between the root canal system and the tooth's attachment apparatus.
Root canal procedures are common. In 1994 alone, some 40 million root canal procedures were performed in the United States. Central to a successful endodontic treatment has been the use of chemicals to enhance canal debridement during cleaning and shaping procedures to facilitate the preparation and complete cleaning of the root canal system. The chemicals used to enhance canal debridement during cleaning and shaping procedures potentially reach all aspects of the root canal system. The most popular chemicals currently used during canal preparation to actively assist in cleaning include bleach, hydrogen peroxide, and chelating agents. Often, a 2%–5% solution of a clear, pale, greenish-yellow strongly alkaline solution of sodium hypochlorite (NaOCl) is used.
During canal preparation, the sodium hypochlorite solution is liberally irrigated into the root canal space where its solvent action facilitates the digestion and removal of pulp and bacteria and the destruction and removal of viruses, spores, endotoxins and other irritants generated by the microorganisms in the canal system as the solution penetrates into all aspects of the root canal system. However, studies have shown that even the most thorough use of sodium hypochlorite does not remove all the material from the root canals. The walls of a root canal are comprised of dentin which contains millions of dentinal tubules per square millimeter, and the irritants can find their way into the tubules of the root canal systems. Thus, after cleaning and shaping procedures, the root canal is still covered with a film of debris, frequently described in the literature as a “smear layer.” This “smear layer” includes dentinal mud and/or organic debris, including the irritants noted above.
The smear layer or film compromises the sealing of the root canal system with gutta percha and root canal sealer. If obturation is incomplete then the root canal space is predisposed to leakage and failure. Post-treatment failures attributable to leakage are common and require endodontic retreatment of the tooth. Thus, for a complete and thorough cleaning, this smear layer or film should be removed. Once the existence of this smear layer was discovered, practitioners began using a weak acid or surfactant, such as 17% EDTA (ethyldiamine-tetraacetic acid), in an effort to remove the smear layer. Typically, the root canal is flushed with EDTA to accomplish this. Some practitioners have been known to use root canal instruments or files to enhance the performance of the EDTA. The files may be manually used or may be mounted in a rotary or vibratory handpiece. Even when files are used, it is difficult to ensure that the file is brought into contact with the complete surface of the root canal, and hence it is difficult to ensure that substantially all of the smear layer has been removed. Additionally, the use of files, especially with a handpiece, leads to iatrogenic events, such as broken instruments, ledges in the wall of the root canal preparation, or even perforation of the root canal system.
In my prior patent, Pat. No. 6,179,617, which is incorporated herein by reference, I disclosed an endodontic brush for use in removing the smear layer. The brush is comprised of a handle, a shank and a brush section extending from the shank. The brush section includes a core with a plurality of bristles extending from the core. The core was made from a pair of twisted wires. While this brush works acceptably, it still has many shortcomings which are due to the fact that the core and shank are made from wire. Each wire from which the core and shank is made is 0.2 mm in diameter, and hence, the core and shank have a diameter of at least 0.4 mm. While the wires are quite thin, once the bristles are added to the core, the brush section has a diameter that is too large to reach to the end of many canals. The wires cannot be made to be thinner because the brush would then become predisposed to breakage during use. Even at the current diameter, the wire shank and core is too flexible. Because of its high flexibility, a practitioner doing an endodontic procedure cannot effectively and purposely brush the sides of the root canal, using the brush in a brushing manner, and hence cannot thoroughly remove the smear layer from the root canal. Additionally, because of the flexibility of the twisted wire core, the brush cannot be driven ultrasonically. The flexibility of the wire core causes too much of the ultrasonic energy to dissipate prior to reaching the bristles of the brush.
Hence, it would be desirable to provide a brush which can reach the ends of the root canal, which is sufficiently flexible to allow the brush to pass around bends in the root canal, and yet which is sufficiently stiff to allow the endodontist to effectively use lateral pressure so the brush can more intimately contact the root canal wall to remove the smear layer.